Ophthalmic laser system

ABSTRACT

An ophthalmic laser system generating a first beam at a wavelength suitable for performing selective laser trabeculoplasty and selectively generating a second beam at a wavelength suitable for performing secondary cataract surgery procedures. The laser system is able to select between directing the first beam or the second beam to the eye of a patient. The first beam is suitably generated at 1064 nm from a Nd:YAG laser and the second beam is frequency doubled to 532 nm in a KTP doubling crystal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of Ser. No. 10/847,062 filed May17, 2004 (incorporated by reference in its entirety for all purposes),which is a continuation-in-part of PCT/AU2003/001224 filed Sep. 18,2003, which claims priority to AU2002951467 filed Sep. 18, 2002.

FIELD OF THE INVENTION

This invention relates to a treatment laser instrument designed for useby ophthalmologists for performing selective laser trabeculoplasty (fortreating glaucoma) procedures and secondary cataract surgery procedures.In particular, the invention relates to an ophthalmic laser system thatcan operate effectively in both the infrared region (for secondarycataract treatment) and other regions, such as the green region (forglaucoma treatment

BACKGROUND TO THE INVENTION

Glaucoma (abnormal intra-ocular pressure) is a major eye problem thatleads to blindness in a significant percentage of the world population.Glaucoma is the most common cause of blindness in the world today. Theestablished technique for treating glaucoma is drug based. Alternativetreatment modalities have been sought to avoid the side effects andnon-specificity associated with drug based treatments. Over the past fewyears a technique known as selective laser trabeculoplasty (SLT) hasbeen invented by Latina. The technique is described in U.S. Pat. No.5,549,596, assigned to The General Hospital Corporation. Latinadescribes the use of a frequency doubled Nd:YAG laser for the SLTprocedure.

SLT is an improvement over a previously used technique referred to asargon laser trabeculoplasty (ALT). ALT uses a thermal effect tocoagulate loose trabecular meshwork cells believed to be present inpatients with glaucoma. Because an Argon laser is essentially CW (ifpulsed, the pulse duration is long compared to thermal transfermechanisms) there is significant heat transfer into surrounding tissue.This results in damage to otherwise healthy cells. It has been foundthat the ALT process can only be used once or twice before collateraldamage prevents any further benefit from ALT treatment.

In contrast, SLT utilizes a pulsed laser (the pulse duration is shortcompared to thermal effects) so there is minimal heat transfer tosurrounding tissue. SLT has been found to be repeatable, unlike the ALTprocess.

A detailed discussion of the SLT modality and a comparison with ALT isfound in Ocular Surgery News published 1 Mar. 2000.

Another very common ophthalmic treatment is secondary cataract surgery.The most effective laser for secondary cataract surgery is a Nd:YAGlaser operating at 1064 nm. These lasers are typically referred to asphotodisruptors as they act by non-thermal mechanisms to cut tissue. Atypical ophthalmic laser system consists of the laser head and a beamdelivery system coupled to a conventional slit lamp assembly. A typicallaser system for secondary cataract surgery is described in U.S. Pat.No. 6,325,792.

At present, two separate laser systems are necessary to perform theprocedures for treating the two most common eye problems.

An attempt to address the problem of requiring multiple lasers fordifferent treatment modalities has been described in U.S. Pat. No.6,066,127. This patent describes a system for changing the laser cavitybetween a pulsed configuration and a continuous wave configuration byintroducing a movable intracavity element. This approach is problematicbecause it is extremely difficult to maintain optimum alignment of thelaser cavity with a movable intracavity element.

A better solution is required.

SUMMARY OF THE INVENTION

In one form, although it need not be the only or indeed the broadestform, the invention resides in an ophthalmic laser system comprising:

a laser module producing a beam of short pulses of radiation with highenergy density at a first wavelength;

a first beam path incorporating an attenuator, beam shaping optics, andmeans for directing the beam at said first wavelength to an eye of apatient;

a second beam path incorporating a frequency conversion module thatconverts the beam at the first wavelength to a beam at a secondwavelength, an attenuator, and means for directing the beam at saidsecond wavelength to the eye of the patient; and

extracavity deflecting means for selectively deflecting the beam at saidfirst wavelength into the second beam path, said means being operablebetween a first position in which the beam at said first wavelengthfollows the first beam path and a second position in which the beam atsaid first wavelength is deflected to said second beam path.

Preferably the beam at said first wavelength is a 1064 nm beam producedby a Nd:YAG laser, and said beam at said second wavelength isfrequency-doubled to 532 nm. The beam is suitably doubled by a KTPdoubling crystal or similar frequency doubling device.

Preferably the extracavity deflecting means comprises a half wave plateand polarizer. The half wave plate is suitably remotely operable, suchas by a servo motor or solenoid.

BRIEF DESCRIPTION OF THE DRAWINGS

To assist in understanding the invention, preferred embodiments will bedescribed with reference to the following figures in which:

FIG. 1 shows a general schematic view of an ophthalmic laser system;

FIG. 2 shows a schematic side view of the photodisruptor optical systemof the ophthalmic laser system in FIG. 1; and

FIG. 3 shows a schematic view of the SLT optical system of theophthalmic laser system in FIG. 1;

FIG. 4 shows a schematic view of the energy monitor system;

FIG. 5 shows a schematic of the beam-shaping module of thephotodisruptor optical system;

FIG. 6 shows a schematic of the beam-shaping module of the SLT opticalsystem; and

FIG. 7 shows an external view of an ophthalmic treatment deviceincorporating the ophthalmic laser system.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown an embodiment of an ophthalmic lasersystem 1 useful for treating glaucoma and secondary cataracts. Thesystem is comprised of a laser module 2, a photodisruptor optical system3 and SLT optical system 4, as shown separately in FIGS. 2 and 3.

The ophthalmic laser system 1 of the present invention combines thephotodisruptor optical system 3 and SLT optical system 4 into oneintegral unit, which uses a single laser module 2. The laser module 2 isa Q switched Nd:YAG laser operating in the infrared spectrum. The laseremits a beam at 1064 nm wavelength, having a pulse width of less than 5nsec. Other laser modules (such as Nd:YLF, Yb:YAG, etc) will also besuitable as will be readily apparent to persons skilled in the art.

Referring now to FIG. 1 and FIG. 2, a pulsed beam from the laser module2 is attenuated at attenuator/beam steering module 5. An energy monitorsystem 6 measures the energy in each pulse. For the photodisruptoroptical system the desired energy density is 0.3-10 mj in an 8-10 μmspot. A half wave plate 7 within the attenuator/beam steering module 5is adjusted to regulate the intensity of the pulsed beam in thephotodisruptor optical system 3. A polarizing plate 8 may deflect thepulsed beam to the SLT optical system 4 depending on the orientation ofthe half wave plate 7. The function of the attenuator/beam steeringmodule 5 will be described in more detail later.

Beam shaping optical module 9 expands the pulsed beam before it travelsup to the folding mirror module 10. The expanded beam is then focused byobjective lens 13 to produce the 8-10 μm beam waist at the treatmentsite which is required to produce photodisruption. An aiming lasermodule 11 provides a continuous, visible laser beam that is split intotwo beams and deflected by folding mirror module 10 to give a targetingreference for the treatment beam. These two aiming laser beams convergewith the pulsed treatment beam at the target site in a patient's eye 12via objective lens 13. An operator 14 views the patient's eye 12 throughthe folding mirror module 10. A safety filter 15 protects the eye of theoperator. The folding mirrors 10 a, 10 b are positioned so that theviewing axis of the operator is not impeded. It will be appreciated bythose skilled in the art that the mirrors may be replaced by prisms orother suitable beam steering optics.

Referring to FIG. 3, the SLT optical system 4 comprises a mirror 16 thatdirects a deflected pulsed beam from the polarizing plate 8 in theattenuator/beam steering module 5 of FIG. 1 to the frequency conversionmodule, which is a frequency doubling module 17 in the preferredembodiment. To maximize frequency doubling efficiency the entire pulsedbeam is deflected by attenuator/beamsteering module 5. The frequencydoubling module 17 converts the output of the laser module to half thewavelength so that the output of the SLT optical system is in thevisible spectrum. For the particular embodiment the Nd:YAG laser moduleoperates in the near infrared at 1064 nm which is frequency doubled to532 nm, which is in the green region of the visible spectrum. The greenpulsed beam is effective in treating glaucoma in patients.

The pulsed green beam may be attenuated at the SLT attenuator 18 toregulate the energy in the pulsed green beam. An energy monitor system19 measures the energy in each pulse. For the SLT process the desiredenergy density is 0.01-5 J/cm², as described by Latina.

Other wavelengths may be suitable for other ophthalmic applications inwhich case the frequency conversion module may triple or quadruple thefundamental frequency. In some applications it may even be desirable touse a tunable frequency conversion module, such as an optical parametricoscillator.

A beam shaping module 20 adjusts the beam profile to provide an evenenergy distribution at the treatment plane. The green beam then travelsto a second folding mirror module 21. A second aiming laser module 22provides a single aiming laser beam which is deflected by the secondfolding mirror 21 and transmitted through folding mirror module 10 andobjective lens 13, as shown in FIG. 1. The continuous visible laseraiming beam generated by the second aiming laser module 22 coincideswith the green pulsed beam at the target site in a patient's eye 12 viaobjective lens 13 and contact lens 23. As mentioned earlier, the mirrorcould be replaced by prisms or other suitable optical elements.

Although two separate aiming laser modules 11, 22 are described, it willbe appreciated that a single aiming laser module could be used withappropriate beam deflecting optics, such as a mirror, to direct theaiming laser beam through folding mirror module 10 for off-axisillumination or folding mirror module 21 for on-axis illumination.

The present invention provides an ophthalmic laser system for treatingglaucoma and secondary cataract conditions, using a single laser source.The present invention integrates two known laser treatment techniques,SLT and photodisruptor, into one integrated system.

The method used to direct the laser beam from the laser module 2 to thephotodisruptor optical system 3 or the SLT optical system 4 will now bedescribed in detail. Referring to FIG. 1, the attenuator/beam steeringmodule 5 first receives a pulsed and linearly polarized beam from lasermodule 2 at half wave plate 7. The pulsed beam passes through the halfwave plate to the polarizing plate 8.

The orientation of the half wave plate 7 determines the amount of thepulsed beam that is passed through the polarizing plate 8 into thephotodisruptor optical system 3. The orientation of the half wave plate7 can be adjusted by motorized means so that the polarization angle ofthe component of the resulting beam which coincides with thetransmission characteristic of the polarizing plate 8 will be passedthrough to the beam shaping module 9. However, as the half wave plate 7is rotated, the polarization of the beam is changed. Accordingly, onlysome portion of the beam will be transmitted.

In the photodisruptor mode for treating secondary cataracts, the halfwave plate 7 is rotated to permit transmission of the required pulsedlaser beam emitted from the laser module 2. If the SLT mode is required,the half wave plate 7 is oriented so that all the beam is reflected fromthe polarising plate 8 to the mirror 16 of the SLT optical system 4.

The ophthalmic laser system described above allows an operator to selectthe mode of treatment to be administered to a patient, simply bychoosing one of two optical paths. A simple adjustment of the half waveplate 7 determines whether a SLT or a photodisruptor mode is chosen fortreating glaucoma or secondary cataracts respectively. The adjustment ofthe half wave plate can be motorized so the selection of treatmentmodality may be by simple button selection.

It will be appreciated that the directing of the Nd:YAG laser beam intothe photodisruptor module path or the SLT module path can be achieved byany suitable means (such as a mirror) but the use of a polarizing plateis preferred.

As mentioned above, each optical system includes an energy monitorsystem in the preferred embodiment. A schematic of the components of anenergy monitor system is shown in FIG. 4. A small percentage of the beamis split by optic plate 24 towards a photodiode 25. A number of filtersand diffusers 26 are positioned in front of the photodiode 25.

As seen in FIG. 2, once the pulse beam is attenuated to the desiredpower, the beam is further conditioned by beam shaping optical module 9.The beam shaping optical module 9 is shown in more detail in FIG. 5.Lenses 27 and 28 form a beam expander which expands the 3 mm diameterbeam from the laser module 2 by ten times. The expanded beam isreflected into the optical viewing path by the folding mirror 10 whichuses a wavelength selective coating to avoid blocking of the viewingpath. The beam from folding mirror 10 is then focused by objective lens13 to produce the 8-10 μm beam waist at the treatment site which isrequired to produce photodisruption .

Referring to FIG. 6, the SLT beam is conditioned by beam shaping module20 before the folding mirror module 21. The beam shaping module 20consists of two lenses 28, 29 that form a beam expander that is designedto produce a well defined treatment spot with an even energydistribution.

The invention is conveniently embodied in an ophthalmic treatment deviceof the type shown in FIG. 7. The treatment device 30 is of theconventional form having a slit lamp assembly 31 mounted on a table 32which is in turn mounted on a height adjusting pedestal 33. The slitlamp assembly 31 is movable with respect to the table 32 +using joystick34, in conventional manner. The ophthalmic laser system is mounted inthe body 35 of the slit lamp assembly 31. This is achieved by using acompact laser cavity and careful placement of optical components.

The ophthalmic laser system is controlled by a control panel 36. The joystick 34 may incorporate a fire button 37 to fire the laser, oralternatively a foot pedal (not shown) may be used.

The invention has been described with reference to one particularembodiment however, it should be noted that other embodiments areenvisaged within the spirit and scope of the invention. For instance,one or two aiming lasers could be used, the photodisruptor or SLT beampath could be selected by a movable mirror, or the beam shaping opticscould have a different configuration.

1-16. (canceled)
 17. A method of treating secondary cataract or glaucomain a patient using an ophthalmic laser system comprising: a lasermodule, which operates to produce a beam of short pulses of radiationwith high energy density at a first wavelength; a first beam path forsecondary cataract treatment and incorporating an attenuator, beamshaping optics, and means for directing the beam of short pulses at saidfirst wavelength to an eye of a patient with secondary cataract; asecond beam path for glaucoma treatment and incorporating a frequencyconversion module that converts the beam of short pulses at the firstwavelength to a beam of short pulses at a second wavelength, anattenuator, and means for directing the beam of short pulses at saidsecond wavelength to an eye of a patient with glaucoma; and anextracavity deflecting means for selectively deflecting the beam ofshort pulses at said first wavelength into the second beam path, saidextracavity deflecting means being operable between a first position inwhich the beam of short pulses at said first wavelength is received byand follows the first beam path and a second position in which the beamof short pulses at said first wavelength is deflected to, received byand follows said second beam path; the method comprising: operating theextracavity deflecting means to select the first or second beam pathdepending on whether the patient has secondary cataract or glaucoma; andoperating the laser system through the selected beam path to treat thepatient.
 18. The method of claim 17, wherein the laser module is anNd:YAG laser which produces the beam of short pulses at the firstwavelength of 1064 nm and the frequency conversion module coverts thebeam of short pulses to the second wavelength of 532 nm.
 19. The methodof claim 17, wherein the extracavity deflecting means comprises arotational half wave plate and polarizer.
 20. The method of claim 19,wherein the rotational half wave plate and the polarizer serve as theattenuator in the first beam path.
 21. The method of claim 19, furthercomprising rotating the rotable half wave plate by motorized meansbetween a first position and a second position to select the first orsecond beam path.
 22. The method of 21, further comprising remotelyselecting between the first positions and the second position.
 23. Themethod of claim 17, wherein the laser module is a flashlamp pumped,solid state laser.
 24. The method of claim 17, wherein the beam shapingoptics in the first beam path comprises a beam expander.
 25. The methodof claim 17, wherein the first beam path further incorporates an energymonitor system.
 26. The method of claim 17, further comprising operatingan aiming laser to provide a targeting reference for the beam at thefirst wavelength.
 27. The method of claim 17, wherein the frequencyconversion module comprises a KTP doubling crystal or similar frequencyconversion device.
 28. The method of claim 17, wherein the second beampath further incorporates an energy monitor system.
 29. The method ofclaim 17, wherein the second beam path further incorporates beam shapingoptics.
 30. The method of claim 17, further comprising operating anaiming laser providing a targeting reference for the beam at the secondwavelength.
 31. The method of claim 17, wherein the laser module isoperated to produce 0.3-10 mJ in an 8-10 μm spot size in the eye of thepatient with secondary cataract when the first beam path is selected andis operated to produce 0.01-5 J/cm² in the eye of the patient withglaucoma when the second beam path is selected.
 32. An ophthalmic lasersystem for selective treatment of glaucoma and/or secondary cataractscomprising: a laser module producing a beam of short pulses of radiationwith high energy density at a first wavelength; a first beam pathincorporating an attenuator, beam shaping optics, and means fordirecting the beam at the first wavelength to an eye of a patient forsecondary cataract treatment; a second beam path incorporating afrequency doubling module that converts the beam at the first wavelengthto a beam at a second wavelength, an attenuator, and means for directingthe beam at the second wavelength to an eye of a patient for glaucomatreatment; extracavity deflecting means for selectively deflecting thebeam at the first wavelength into the second beam path, said means beingoperable between a first position in which the beam at the firstwavelength follows the first beam path and a second position in whichthe beam at the first wavelength is deflected to the second beam path;and means for remotely selecting between said first beam path forsecondary cataract treatment and said second beam path for glaucomatreatment.
 33. The ophthalmic laser system of claim 32, wherein thelaser module is a flashlamp pumped, solid state laser.
 34. Theophthalmic laser system of claim 32, wherein the laser module is aNd:YAG laser producing said beam at the first wavelength at a wavelengthof 1064 nm, and said beam at the second wavelength is frequency-doubledto 532 nm.
 35. The ophthalmic laser system of claim 32, wherein the beamshaping optics in the first beam path comprises a beam expander.
 36. Theophthalmic laser system of claim 32, wherein the first beam path furtherincorporates an energy monitor system.
 37. The ophthalmic laser systemof claim 32, further comprising an aiming laser providing a targetingreference for the beam at the first wavelength.
 38. The ophthalmic lasersystem of claim 32, wherein the frequency doubling module comprises aKTP doubling crystal or similar frequency doubling device.
 39. Theophthalmic laser system of claim 32, wherein the second beam pathfurther incorporates an energy monitor system.
 40. The ophthalmic lasersystem of claim 32, wherein the second beam path further incorporatesbeam shaping optics.
 41. The ophthalmic laser system of claim 32,further comprising an aiming laser providing a targeting reference forthe beam at the second wavelength.
 42. The ophthalmic laser system ofclaim 32, wherein the extracavity deflecting means comprises a half waveplate and polarizer.
 43. The ophthalmic laser system of claim 42,wherein the half wave plate is rotatable by motorized means.
 44. Theophthalmic laser system of claim 42, wherein the half wave plate isremotely operable.
 45. An ophthalmic laser system comprising: a Nd:YAGlaser module producing a beam of short pulses of radiation with highenergy density at a first wavelength; a first beam path incorporating anattenuator, beam shaping optics, and means for directing the beam atsaid first wavelength to an eye of a patient with secondary cataract; asecond beam path incorporating a frequency doubling module that convertsthe beam at the first wavelength to a beam at a second wavelength, anattenuator, and means for directing the beam at said second wavelengthto an eye of a patient with glaucoma; and extracavity deflecting meansfor selectively deflecting the beam at said first wavelength into thesecond beam path, said means being operable between a first position inwhich the beam at said first wavelength follows the first beam path anda second position in which the beam at said first wavelength isdeflected to said second beam path; wherein said first wavelength isnominally 1064 nm and is for secondary cataract treatment and saidsecond wavelength is nominally 532 nm and is for glaucoma treatment.